Progressive power lens and eye glass lens

Abstract

A progressive power lens provides a large clear vision area from a far-distance use section to a progressive section, wherein an astigmatism imbalance during vision through both eyes is eliminated, and eye movement between far and near distance use takes place smoothly. Astigmatism is distributed asymmetrically in the progressive region of the progressive power lens with respect to a meridian in such manner that a larger astigmatism occurs in a nose-side region than in an ear-side region. By so doing, distribution of astigmatism in the nose-side progressive region is eased to match that of the ear-side progressive region. Moreover, by making the increasing ratio beta of the astigmatism in the far-near direction milder than the increasing ratio alpha of the astigmatism in the left-right direction, a large clear vision area is obtained and the astigmatism imbalance during vision with both eyes is eliminated. Moreover, eye movement between the far-distance use and near-distance use takes place smoothly.

What is claimed is: 
     
       1. A progressive power lens for eye glasses comprising: a far-distance use section having a first refracting power;   a near-distance use section having a second refracting power;   a progressive section between the far-distance use section and the near-distance use section having a progressive refracting power; and   a meridian section in which an astigmatism becomes nearly zero, the meridian section crossing substantially a center of the far-distance use section and a center of the near-distance use section, the meridian section being displaced towards a nose side of the eye glasses to accommodate a convergence between the progressive section and the near-distance use section wherein the astigmatism occurs in both the nose side and an ear side of the far-distance use section and a distribution of the astigmatism in the far-distance use section is asymmetric with respect to the meridian section.   
     
     
       2. The progressive power lens of claim 1 wherein the far-distance use section, the near-distance use section and the progressive section are formed on any one surface of the progressive power lens, the meridian section is a meridian having several centers of curvature and the curvature of the far-distance use section changes asymmetrically with respect to the meridian. 
     
     
       3. The progressive power lens of claim 1 wherein the far-distance use section comprises a first section in which the astigmatism increases along a direction from the meridian section to a nose-side of the lens and a second section in which the astigmatism increases along a direction from the meridian section to an ear-side of the lens, and the astigmatism in the first section is larger than the astigmatism in the second section measured at respective points which are nearly equidistant from the meridian section. 
     
     
       4. The progressive power lens of claim 1, wherein the lens is shaped to fit an eye glass frame. 
     
     
       5. A progressive power lens for eye glasses comprising: a far-distance use section having a first refracting power;   a near-distance use section having a second refracting power;   a progressive section between the far-distance use section and the near-distance section having a progressive refracting power; and   a meridian section in which astigmatism becomes nearly zero, the meridian section crossing substantially a center of the far-distance use section and the near-distance use section, the meridian section being displaced towards a nose side of the lens between the progressive section and the near-distance use section to accommodate a convergence, wherein an astigmatism increase ratio k is nearly 1.5 or larger and k=α/β where α is an astigmatism increase ratio in a first direction substantially perpendicular to the meridian section and extending from nearly a center of the near-distance use section to an ear side of the lens, and β is an astigmatism increase ratio in a second direction being 15 to 20 cm away from the meridian section and extending from near a center of the progressive power lens to the near-distance use section substantially parallel to the meridian section.   
     
     
       6. The progressive power lens of claim 5 wherein the astigmatism increase ratio k is substantially in the range of 1.5 to 5. 
     
     
       7. The progressive power lens of claim 5 wherein the astigmatism increase ratio k is substantially in the range of 2 to 4. 
     
     
       8. The progressive power lens of claim 5 wherein the astigmatism increase ratio k is substantially in the range of 2 to 3. 
     
     
       9. The progressive power lens of claim 5 wherein the far-distance use section contains a section in which astigmatism occurs and a distribution of astigmatism in the far-distance use section is asymmetric with respect to the meridian section. 
     
     
       10. The progressive power lens of claim 5, wherein the lens is shaped to fit an eye glass frame.